A boy displaced from the Red Sea port city of Hodeidah sits outside a house where he and his family live in the outskirts of Sana’a. Photograph: Khaled Abdullah/Reuters

The besieged port city of Hodeidah in Yemen has become a “ghost town” as residents continue to flee in their thousands, using the current lull in hostilities to sell what remains of their belongings and escape amid fears UN-brokered negotiations will collapse.

Aid workers have told the Guardian that although things seem peaceful as diplomatic talks continue between warring parties, schools and businesses remain closed, and “anyone with any resources to get out is doing so now”.

“People are living in pathetic conditions not fit for humans and completely untenable for those who are most vulnerable,” said Isaac Ooko, area manager in Hodeidah for the Norwegian Refugee Council (NRC).

“What might appear to be a pause to the outside world doesn’t feel the same for those of us seeing what it means for people here.”

More than 35,000 families have been displaced from Hodeidah governorate since June, when the Saudi-led coalition began a military offensive to wrest control of the vital Red Sea port city from Iran-backed Houthi rebels.

UN-led negotiations, brokered by special envoy Martin Griffiths, have floated the idea of handing over Hodeidah – which handles about 70% of all Yemen’s imports – to UN supervision, in a bid to end current blockages on food, water and oil.

The hiatus has allowed much-needed supplies to come back into the famine-stricken country, where 22 million people – 80% of the entire population – need humanitarian aid.

But aid workers warn supplies are low, with current food stocks at only 40% and fuel at just 16% of July’s requirements.

“It’s very easy for food to come in overland, but the biggest problem is the fuel,” said NRC’s advocacy adviser Suze van Meegan by phone from the capital, Sana’a.

People are living in pathetic conditions not fit for humans

Isaac Ooko

“Without enough fuel, hospitals won’t be able to use their generators, water systems requiring pumps will start breaking down and the risk of cholera reemerging is a very real one – it would only take two or three days of no water for things to really explode.”

Dina El-Mamoun, head of policy and advocacy at Oxfam International Yemen, said many people who want to leave do not have the money to do so, and “some of those who have sought to flee have fallen victims to landmines”.

She added: “The fighting in the southern part of Hodeidah in particular continues to intensify, as military enforcements were said to have been sent to Tuhaita area in Hodeidah in the last couple of days. Locals are talking of thousands of people effectively trapped in those areas.”

Families are reduced to eating one meal a day, she said. There are also reports that renal treatment centres are running out of medical supplies.

Aid workers warned against seeing the break in aggression in the port city as an indication of nationwide peace, pointing to continued fighting in districts south of the city, such as At Tuhayat and Zabid.

Airstrikes north of the northern city of Sa’ada, combined with ground troops moving down towards Hodeidah, have pushed a steady stream of people to seek safety in Hajjah, where aid teams claim civilians are arriving in temperatures of 40C desperate for water, with only the items they can carry.

Those who remain in Hodeidah question whether the current pause is just the calm before the storm.

“We’ve been watching this situation develop over the last one to two years but this is the point at which we feel the least certain about what will happen next,” said van Meegan.

“We fully support and endorse everything being done by the special envoy and are inclined now to see it as the only hope for maintaining peace in Hodeidah. If that process falls apart at any point, for any reason, it is very hard to say what will happen.”